Water saving irrigation improves the solubility and bioavailability of zinc in rice paddy

Abstract

Fields experiment was done to investigate the effect of a typical water saving irrigation technique, namely non-flooding controlled irrigation (NFI), on the extractability, solubility, and bioavailability of zinc (Zn) in a non-polluted paddy soil. The Zn contents in the soil solutions, soil extractions by modified BCR (European Community Bureau of Reference) sequential extraction procedure, and the plant digestions were measured. Compared with the Zn in flooding irrigation (FI) soil, Zn contents in extractable (EXT) form and Zn contents in soil solutions was increased in 0-20 cm NFI soil, accompanied with a little reduction of soil Zn in oxidizable (OXD) form. That confirmed the Zn in OXD form was released into soil solution under the wetting-drying cycle condition in NFI fields, and hence resulted in high extractability and solubility of Zn in top surface soil. As a result, Zn contents in the rice plant parts in NFI fields were higher than in FI fields. It can be concluded that NFI irrigation is help to enhance soil Zn bioavailability and food Zn nutrients status in the soil without Zn-pollution and Zn deficiency, but might led to soil Zn depletion in Zn deficient soil or rice foodstuffs pollution in Zn-polluted soil.